This Program Project, entitled "Coordinated Studies in Rheumatic Diseases" has been the focus of the clinical and experimental studies within the Division of Clinical Immunology and Rheumatology, University of Alabama in Birmingham for the last several years. The three major areas to be investigated during the term of this current proposal are the following: 1. A determination of the structure of cell surface antigens. These antigens are felt to be genetically determined and model systems will be evaluated in examination of mouse lymphoblastoid cells. Later, comparisons will be made with genetic markers on the surface of human lymphoblastoid cells obtained from peripheral blood or established cell culture lines. 2. An investigation of the genetic control, expression and regulation of complement components. These will be approached from the standpoint of animal model systems as well as human complement components obtained from the serum of normal individuals and from individuals with selected complement deficiencies. 3. A determination of the role of circulating immune complexes in patients with rheumatic diseases. These will be approaches through an application of some newly established in vitro tests to evaluate and correlate the presence of immune complexes with clinical rheumatic disease syndrome. All of these investigations will be organized and interrelated at the level of understanding the molecular parameters responsible for genetic correlates of host response to rheumatic diseases.